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#1
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Tektronix 2445, No EHT , oscillator board 'failed' common ?
Tektronix 2445, No EHT , oscillator board 'failed' common faults ?
After many years of use, the scopes failed .. Everything was fine, then lost the trace....On checking, the 750 mA fuse on the -15v un-reg line had blowen, turns out the A9 , eht oscillator board is drawing excess current .not oscillating .. no signe of anything over heated ... scope powers up fine with A9 board 'out' looks to pass all self tests Q are there any 'common' fail's for this board , the power transistor looks to be giving 'odd' reading's and ive ordered one to replace it .. are there any other components that are know to 'fail' ? Tnx Graham .. |
#2
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Tektronix 2445, No EHT , oscillator board 'failed' common ?
Graham wrote in
ups.com: Tektronix 2445, No EHT , oscillator board 'failed' common faults ? You mean you have "no HV". It happens. After many years of use, the scopes failed .. Everything was fine, then lost the trace....On checking, the 750 mA fuse on the -15v un-reg line had blowen, turns out the A9 , eht oscillator board is drawing excess current .not oscillating .. no signe of anything over heated could be a bad multipler,or a bad CRT(anode loading problem) Disconnect the xfmr drive to the multiplier,see if current draw is too high. .. scope powers up fine with A9 board 'out' looks to pass all self tests Q are there any 'common' fail's for this board , the power transistor looks to be giving 'odd' reading's and ive ordered one to replace it .. are there any other components that are know to 'fail' ? Tnx Graham .. try unplugging the CRT anode lead,see if the scope powers up with it disconnected. CRTs do fail and overload the multiplier. -- Jim Yanik jyanik at kua.net |
#3
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Tektronix 2445, No EHT , oscillator board 'failed' common ?
On Aug 21, 7:36 pm, Jim Yanik wrote:
Graham wrote roups.com: Tektronix 2445, No EHT , oscillator board 'failed' common faults ? You mean you have "no HV". It happens. After many years of use, the scopes failed .. Everything was fine, then lost the trace....On checking, the 750 mA fuse on the -15v un-reg line had blowen, turns out the A9 , eht oscillator board is drawing excess current .not oscillating .. no signe of anything over heated could be a bad multipler,or a bad CRT(anode loading problem) Disconnect the xfmr drive to the multiplier,see if current draw is too high. .. scope powers up fine with A9 board 'out' looks to pass all self tests Q are there any 'common' fail's for this board , the power transistor looks to be giving 'odd' reading's and ive ordered one to replace it .. are there any other components that are know to 'fail' ? Tnx Graham .. try unplugging the CRT anode lead,see if the scope powers up with it disconnected. CRTs do fail and overload the multiplier. -- Jim Yanik jyanik at kua.net Ok Jim, Thanks for the reply, by what you say, i assume the switching transistor is not the first item to suspect ? With the board 'in' as soon as power is applied. the 750 ma fuse blows , i dident see any oscillation , looks to be quite a load as it pulls the -15v down to -12 (shows -19 with board 'out') - Tube ?, I could try with the cable off , but The oscillator is not running and none of the tube voltages exist ... for that test would need the ocillator running before you could 'load it' ? Tnx Graham . |
#4
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Tektronix 2445, No EHT , oscillator board 'failed' common ?
Graham wrote in
ups.com: On Aug 21, 7:36 pm, Jim Yanik wrote: Graham wrote roups.com: Tektronix 2445, No EHT , oscillator board 'failed' common faults ? You mean you have "no HV". It happens. After many years of use, the scopes failed .. Everything was fine, then lost the trace....On checking, the 750 mA fuse on the -15v un-reg line had blowen, turns out the A9 , eht oscillator board is drawing excess current .not oscillating .. no signe of anything over heated could be a bad multipler,or a bad CRT(anode loading problem) Disconnect the xfmr drive to the multiplier,see if current draw is too high. .. scope powers up fine with A9 board 'out' looks to pass all self tests Q are there any 'common' fail's for this board , the power transistor looks to be giving 'odd' reading's and ive ordered one to replace it .. are there any other components that are know to 'fail' ? Tnx Graham .. try unplugging the CRT anode lead,see if the scope powers up with it disconnected. CRTs do fail and overload the multiplier. -- Jim Yanik jyanik at kua.net Ok Jim, Thanks for the reply, by what you say, i assume the switching transistor is not the first item to suspect ? I've seen more HV multipliers fail than HV oscillator xstrs. (it's not a "switching" xstr,it does not turn hard OFF.) With the board 'in' as soon as power is applied. the 750 ma fuse blows , i dident see any oscillation , looks to be quite a load as it pulls the -15v down to -12 (shows -19 with board 'out') Too much of a load,and the oscillator never starts.But it does pull a lot of current,enough to blow the fuse.Of course,shorted HV caps or bad diodes can also be a problem. But it's easiest to pull the anode lead first,and then to isolate the multiplier. - Tube ?, I could try with the cable off ANODE lead,the red one.Don't bother with the CRT socket at the back end. If you pull the CRT anode lead and get a big spark when shorting it's plug to chassis,then the multiplier and CRT are probably OK. , but The oscillator is not running and none of the tube voltages exist ... for that test would need the ocillator running before you could 'load it' ? Tnx Graham . Do you have a service manual with schematics??? The circuit descriptions are very valuable,2nd only to the schematics themselves. -- Jim Yanik jyanik at kua.net |
#5
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Tektronix 2445, No EHT , oscillator board 'failed' common ?
On Aug 21, 11:36 pm, Jim Yanik wrote:
Graham wrote roups.com: On Aug 21, 7:36 pm, Jim Yanik wrote: Graham wrote roups.com: Tektronix 2445, No EHT , oscillator board 'failed' common faults ? You mean you have "no HV". It happens. After many years of use, the scopes failed .. Everything was fine, then lost the trace....On checking, the 750 mA fuse on the -15v un-reg line had blowen, turns out the A9 , eht oscillator board is drawing excess current .not oscillating .. no signe of anything over heated could be a bad multipler,or a bad CRT(anode loading problem) Disconnect the xfmr drive to the multiplier,see if current draw is too high. .. scope powers up fine with A9 board 'out' looks to pass all self tests Q are there any 'common' fail's for this board , the power transistor looks to be giving 'odd' reading's and ive ordered one to replace it .. are there any other components that are know to 'fail' ? Tnx Graham .. try unplugging the CRT anode lead,see if the scope powers up with it disconnected. CRTs do fail and overload the multiplier. -- Jim Yanik jyanik at kua.net Ok Jim, Thanks for the reply, by what you say, i assume the switching transistor is not the first item to suspect ? I've seen more HV multipliers fail than HV oscillator xstrs. (it's not a "switching" xstr,it does not turn hard OFF.) With the board 'in' as soon as power is applied. the 750 ma fuse blows , i dident see any oscillation , looks to be quite a load as it pulls the -15v down to -12 (shows -19 with board 'out') Too much of a load,and the oscillator never starts.But it does pull a lot of current,enough to blow the fuse.Of course,shorted HV caps or bad diodes can also be a problem. But it's easiest to pull the anode lead first,and then to isolate the multiplier. - Tube ?, I could try with the cable off ANODE lead,the red one.Don't bother with the CRT socket at the back end. If you pull the CRT anode lead and get a big spark when shorting it's plug to chassis,then the multiplier and CRT are probably OK. , but The oscillator is not running and none of the tube voltages exist ... for that test would need the ocillator running before you could 'load it' ? Tnx Graham . Do you have a service manual with schematics??? The circuit descriptions are very valuable,2nd only to the schematics themselves. -- Jim Yanik jyanik at kua.net- Hide quoted text - - Show quoted text - Some progress... Found one fault, that was the soldered joint , center pin of the switching transistor had failed , re made that and the oscillator started running Supply current 1.3 Amps , test wavefoem voltages all low , approx 50 % , sine waves clipped. Tried disconnecting tube anode connector after running, tube produced about 4 mm spark to earth. Removed , two , connections from tags , rear of transformer to 'eht' module , Supply current reduced to 450 mA . waveforms 'ok' re-connected 'upper' lead, (near qty 6 trim pots) slight increase supply current . waveform's 'ok' Re-connected 'lower' connection , supply current increrased to 1.3 Amps , wave forms low. Not sure if lower connection is the anode or cathode (no pin numbers) voltage source, either way, it looks like the 'eht block' has failed .... .... who would have one of those ? Tnx Graham .. |
#6
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Tektronix 2445, No EHT , oscillator board 'failed' common ?
On Aug 26, 11:12 pm, Graham wrote:
On Aug 21, 11:36 pm, Jim Yanik wrote: Graham wrote roups.com: On Aug 21, 7:36 pm, Jim Yanik wrote: Graham wrote roups.com: Tektronix 2445, No EHT , oscillator board 'failed' common faults ? You mean you have "no HV". It happens. After many years of use, the scopes failed .. Everything was fine, then lost the trace....On checking, the 750 mA fuse on the -15v un-reg line had blowen, turns out the A9 , eht oscillator board is drawing excess current .not oscillating .. no signe of anything over heated could be a bad multipler,or a bad CRT(anode loading problem) Disconnect the xfmr drive to the multiplier,see if current draw is too high. .. scope powers up fine with A9 board 'out' looks to pass all self tests Q are there any 'common' fail's for this board , the power transistor looks to be giving 'odd' reading's and ive ordered one to replace it .. are there any other components that are know to 'fail' ? Tnx Graham .. try unplugging the CRT anode lead,see if the scope powers up with it disconnected. CRTs do fail and overload the multiplier. -- Jim Yanik jyanik at kua.net Ok Jim, Thanks for the reply, by what you say, i assume the switching transistor is not the first item to suspect ? I've seen more HV multipliers fail than HV oscillator xstrs. (it's not a "switching" xstr,it does not turn hard OFF.) With the board 'in' as soon as power is applied. the 750 ma fuse blows , i dident see any oscillation , looks to be quite a load as it pulls the -15v down to -12 (shows -19 with board 'out') Too much of a load,and the oscillator never starts.But it does pull a lot of current,enough to blow the fuse.Of course,shorted HV caps or bad diodes can also be a problem. But it's easiest to pull the anode lead first,and then to isolate the multiplier. - Tube ?, I could try with the cable off ANODE lead,the red one.Don't bother with the CRT socket at the back end. If you pull the CRT anode lead and get a big spark when shorting it's plug to chassis,then the multiplier and CRT are probably OK. , but The oscillator is not running and none of the tube voltages exist ... for that test would need the ocillator running before you could 'load it' ? Tnx Graham . Do you have a service manual with schematics??? The circuit descriptions are very valuable,2nd only to the schematics themselves. -- Jim Yanik jyanik at kua.net- Hide quoted text - - Show quoted text - Some progress... Found one fault, that was the soldered joint , center pin of the switching transistor had failed , re made that and the oscillator started running Supply current 1.3 Amps , test wavefoem voltages all low , approx 50 % , sine waves clipped. Tried disconnecting tube anode connector after running, tube produced about 4 mm spark to earth. Removed , two , connections from tags , rear of transformer to 'eht' module , Supply current reduced to 450 mA . waveforms 'ok' re-connected 'upper' lead, (near qty 6 trim pots) slight increase supply current . waveform's 'ok' Re-connected 'lower' connection , supply current increrased to 1.3 Amps , wave forms low. Not sure if lower connection is the anode or cathode (no pin numbers) voltage source, either way, it looks like the 'eht block' has failed .... ... who would have one of those ? Tnx Graham ..- Hide quoted text - - Show quoted text - Part number from manual A9 VR 1830 152-0805-00 MF CODE 80009 HV MULT 20KV Tnx - G .. |
#7
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Tektronix 2445, No EHT , oscillator board 'failed' common ?
Graham wrote in
oups.com: Found one fault, that was the soldered joint , center pin of the switching transistor had failed , re made that and the oscillator started running Supply current 1.3 Amps , test wavefoem voltages all low , approx 50 % , sine waves clipped. Tried disconnecting tube anode connector after running, tube produced about 4 mm spark to earth. Removed , two , connections from tags , rear of transformer to 'eht' module , Supply current reduced to 450 mA . waveforms 'ok' re-connected 'upper' lead, (near qty 6 trim pots) slight increase supply current . waveform's 'ok' Re-connected 'lower' connection , supply current increrased to 1.3 Amps , wave forms low. Not sure if lower connection is the anode or cathode (no pin numbers) voltage source, either way, it looks like the 'eht block' has failed .... ... who would have one of those ? Tnx Graham ..- Hide quoted text - - Show quoted text - Part number from manual A9 VR 1830 152-0805-00 MF CODE 80009 HV MULT 20KV Tnx - G .. http://www.sphere.bc.ca/test/tek-parts/tekparts5.html they have a used "as-is" one for $55 USD. -- Jim Yanik jyanik at kua.net |
#8
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Tektronix 2445, No EHT , oscillator board 'failed' common ?
On Aug 27, 12:17 am, Jim Yanik wrote:
Graham wrote groups.com: Found one fault, that was the soldered joint , center pin of the switching transistor had failed , re made that and the oscillator started running Supply current 1.3 Amps , test wavefoem voltages all low , approx 50 % , sine waves clipped. Tried disconnecting tube anode connector after running, tube produced about 4 mm spark to earth. Removed , two , connections from tags , rear of transformer to 'eht' module , Supply current reduced to 450 mA . waveforms 'ok' re-connected 'upper' lead, (near qty 6 trim pots) slight increase supply current . waveform's 'ok' Re-connected 'lower' connection , supply current increrased to 1.3 Amps , wave forms low. Not sure if lower connection is the anode or cathode (no pin numbers) voltage source, either way, it looks like the 'eht block' has failed .... ... who would have one of those ? Tnx Graham ..- Hide quoted text - - Show quoted text - Part number from manual A9 VR 1830 152-0805-00 MF CODE 80009 HV MULT 20KV Tnx - G .. http://www.sphere.bc.ca/test/tek-parts/tekparts5.html they have a used "as-is" one for $55 USD. -- Jim Yanik jyanik at kua.net- Hide quoted text - - Show quoted text - Ok Thanks for the link Jim, Ive asked for a shipping price to the UK .. thought I had found the problem when I spotted the failed solder joint on the center pin of the transister ! scope did have a odd fault , now and agen, at low trace speeds it looked as if it was being Z moded by a pulse gen .. must of been the joint arcing .. luckly the telequipment s54a keeps working ! G .. |
#9
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Tektronix 2445, No EHT , oscillator board 'failed' common ?
On Aug 27, 12:42 am, Graham wrote:
On Aug 27, 12:17 am, Jim Yanik wrote: Graham wrote groups.com: Found one fault, that was the soldered joint , center pin of the switching transistor had failed , re made that and the oscillator started running Supply current 1.3 Amps , test wavefoem voltages all low , approx 50 % , sine waves clipped. Tried disconnecting tube anode connector after running, tube produced about 4 mm spark to earth. Removed , two , connections from tags , rear of transformer to 'eht' module , Supply current reduced to 450 mA . waveforms 'ok' re-connected 'upper' lead, (near qty 6 trim pots) slight increase supply current . waveform's 'ok' Re-connected 'lower' connection , supply current increrased to 1.3 Amps , wave forms low. Not sure if lower connection is the anode or cathode (no pin numbers) voltage source, either way, it looks like the 'eht block' has failed .... ... who would have one of those ? Tnx Graham ..- Hide quoted text - - Show quoted text - Part number from manual A9 VR 1830 152-0805-00 MF CODE 80009 HV MULT 20KV Tnx - G .. http://www.sphere.bc.ca/test/tek-parts/tekparts5.html they have a used "as-is" one for $55 USD. -- Jim Yanik jyanik at kua.net- Hide quoted text - - Show quoted text - Ok Thanks for the link Jim, Ive asked for a shipping price to the UK .. thought I had found the problem when I spotted the failed solder joint on the center pin of the transister ! scope did have a odd fault , now and agen, at low trace speeds it looked as if it was being Z moded by a pulse gen .. must of been the joint arcing .. luckly the telequipment s54a keeps working ! G ..- Hide quoted text - - Show quoted text - ++ Thanks for help, changed a9 board scope up and running ++ still problem with trace intensity at low tb speeds .. G .. |
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